As a vehicle decelerates to a stop whilst traversing terrain having a deformable, low-mu surface (e.g., sand, gravel, mud, or wet grass,) the wheels of the vehicle may dig or sink into the soft surface of the terrain. The digging or sinking of the vehicle wheels may be compounded or made worse by the pitching of the vehicle—and therefore, the transfer of the vehicle weight—toward the front wheels of the vehicle as the vehicle decelerates (i.e., a greater vertical force is applied to the front wheels of the vehicle). The extent to which the wheels dig/sink into the surface may be dependent upon a number of factors, such as, for example, the speed of the vehicle, the gradient (i.e., incline) of the terrain the vehicle is traversing, the weight of the vehicle, the size (e.g., footprint) and/or pressure of the tyres, and the demanded brake torque, to cite a few possibilities. For example, when a relatively high demanded brake torque is applied the vehicle wheels, for example a demanded brake torque typically used to decelerate a vehicle on a high-mu surface (e.g., tarmac or pavement), the vehicle wheels may dig/sink relatively deeply into the surface, for example in very soft surfaces such as dry sand the wheels may dig in up to the rims on which the vehicle's tires are mounted, or more.
As the vehicle wheels dig/sink into the surface, a drag torque may be applied to the wheels that has a decelerating effect on the vehicle. The combination of the demanded brake torque and the decelerating drag torque caused by the digging/sinking of the wheels may cause the vehicle to decelerate and, in certain instances, abruptly stop in an uncomposed manner.
Additionally, as the vehicle wheels dig/sink into the surface, a substantial amount of surface material (e.g., sand, gravel, mud, etc) may build-up in front of the vehicle wheels. This build-up of material may make it more difficult to subsequently pull away in a composed manner since the vehicle must first overcome the build-up of material before progressing as desired.
Accordingly, it is an aim of the present invention to address, for example, the disadvantages identified above.